The present invention relates to abrasive saw blades or cutting wheels and, most specifically to saw blades of the type formed by a strong, circular sheet metal drive core having one or more cutting members containing dispersed diamond dust secured around its periphery by a metallic bond and suitable for serious industrial applications.
Diamond abrasive saws of the metallic bonded variety have been classicially divided into three distinct groups, all of which are well known in the trade at the present time. The first of these groups is the serrated or notched rim type blade, which is old in the art and is probably the earliest concept of the diamond cutting disc or saw. This type of blade is made by notching or slitting a disc of steel or copper and inserting into these fine hacks a paste of diamond grit and a holding material like petroleum jelly or, more recently, various metal powders. The notched rim type of saw has the merit of being reasonably indestructible, but it cuts so poorly that it has no real acceptance in any serious industrial applications, although it is satisfactory in the case of the lowest priced blades which are used in home hobby-type operations such as the lapidary avocation.
The second group of saw blades consists of a cutting disc having around its periphery a continuous annulus of compressed and matured metallic powder containing diamond dust. This blade has been traditionally made by cold molding the metal powder and diamond dust annulus around a steel body and sintering or otherwise maturing the annulus to a sufficient strength to hold the diamond dust well and to cut freely. This type of blade is functionally superior over the first mentioned group of blades, but it too is unsatisfactory for serious industrial applications since it has the disadvantage of being physically frail due to the delicate nature of the bond between the annulus and the core. Various mechanical devices have been proposed to improve the bond, but in general due to the shortcomings of the manufacturing method, the cutting disc so made is fragile. Its use is confined in large part to precision operations such as germanium cutting, optical glass cutting, and other such uses that fall more or less into the instrument making classes.
The third and relatively recent group of saw blades is the discontinuous rim or segmental type. This cutting disc is made by manufacturing a series of short arcuate segments containing diamond powder in a metallic body. These segments are usually about 2 inches long and are ordinarily silver soldered, brazed or welded to the rim of a steel core which has been divided into sections of approximately the segment length by chopping or sawing the rim radially. Without these discontinuities, the saw disc could not readily be made owing to the great stresses created in the disc by heating only its periphery. The segmented blade has been accepted by those fields that are prone to give the hardest usage to the blades, such as the concrete sawing and masonry cutting field where rough abrasive cutting is done.
For such applications it is common to flush the cutting area continuously during the cutting operation with a fluid coolant in order to keep the blade as cool as possible and to flush from such area loose rock-like material, spent abrasive and the like, all of which in combination with the coolant itself is generally referred to in the art and throughout this description of the present invention as "swarf". Even though the construction of this type of blade has been developed to a high point of perfection, blades must commonly be replaced whenever the swarf erodes the steel drive core at the juncture of the cutting members with the core and thus causes undercutting of the cutting members and possible loss of the cutting members. This is particularly the case in certain types of concrete cutting operations. Prior to the invention of the related application referred to above, little or no thought had been given to the idea of utilizing the blade construction itself to create a more effective means of providing greater cooling of the wheel and delivering coolant to the immediate area or point at which the wheel is making the cut as a means of flushing the swarf from that portion of the cut or cut groove which overlaps the sides of the wheel as the cut is being made.
Another recently developed segmental blade or cutting wheel is that disclosed in the above-referenced copending patent application of Paul B. Ballenger, Ser. No. 403,200, filed on July 29, 1982 and assigned to the same assignee as the present invention, the disclosure of said copending application being incorporated by reference herein. Although such segmental cutting wheel represents a major advancement in the art, the present invention provides even more effective means of cooling the wheel, of delivering coolant to the cutting portion of the wheel, and of flushing the swarf from the portion of the cut that overlaps the sides of the wheel during the cutting operation.